The invention relates in general to driveshaft assemblies, such as are commonly found in the drive train systems of most vehicles. In particular, this invention relates to an improved structure for a sliding spline type of slip joint for use in such a vehicular driveshaft assembly.
Drive train systems are widely used for generating power from a source and for transferring such power from the source to a driven mechanism. Frequently, the source generates rotational power, and such rotational power is transferred from the source to a rotatably driven mechanism. For example, in most land vehicles in use today, an engine/transmission assembly generates rotational power, and such rotational power is transferred from an output shaft of the engine/transmission assembly through a driveshaft assembly to an input shaft of an axle assembly so as to rotatably drive the wheels of the vehicle. To accomplish this, a typical driveshaft assembly includes a hollow cylindrical driveshaft tube having a pair of end fittings, such as a pair of tube yokes, secured to the front and rear ends thereof. The front end fitting forms a portion of a front universal joint that connects the output shaft of the engine/transmission assembly to the front end of the driveshaft tube. Similarly, the rear end fitting forms a portion of a rear universal joint that connects the rear end of the driveshaft tube to the input shaft of the axle assembly. The front and rear universal joints provide a rotational driving connection from the output shaft of the engine/transmission assembly through the driveshaft tube to the input shaft of the axle assembly, while accommodating a limited amount of angular misalignment between the rotational axes of these three shafts.
Not only must a typical drive train system accommodate a limited amount of angular misalignment between the source of rotational power and the rotatably driven device, but it must also typically accommodate a limited amount of relative axial movement therebetween. For example, in most vehicles, a small amount of relative axial movement frequently occurs between the engine/transmission assembly and the axle assembly when the vehicle is operated. To address this, it is known to provide a slip joint in the driveshaft assembly. A typical slip joint includes first and second members that have respective structures formed thereon that cooperate with one another for concurrent rotational movement, while permitting a limited amount of axial movement to occur therebetween.
A typical sliding spline type of slip joint includes male and female members having respective pluralities of splines formed thereon. The male member is generally cylindrical in shape and has a plurality of outwardly extending splines formed on the outer surface thereof. The male member may be formed integrally with or secured to a first end of the driveshaft assembly described above. The female member, on the other hand, is generally hollow and cylindrical in shape and has a plurality of inwardly extending splines formed on the inner surface thereof. The female member may be formed integrally with or secured to a second end of the driveshaft assembly described above. To assemble the slip joint, the male member is inserted within the female member such that the outwardly extending splines of the male member cooperate with the inwardly extending splines of the female member. As a result, the male and female members are connected together for concurrent rotational movement. However, the outwardly extending splines of the male member can slide relative to the inwardly extending splines of the female member to allow a limited amount of relative axial movement to occur between the engine/transmission assembly and the axle assembly of the drive train system.
One problem that has been experienced with sliding spline type of slip joints is that undesirable radially extending gaps can exist between cooperating splines provided on the male and female members thereof. These gaps can occur as a result of manufacturing tolerances in the formation of the male and female splined members and usually result in an undesirable amount of looseness therebetween during operation. Such looseness can allow the splined members to extend at a slightly cantilevered angle relative to one another, a condition that is often referred to a broken back. Known solutions to the problems of broken back have been found to be relatively difficult, costly, and time consuming to employ. Thus, it would be desirable to provide an improved structure for a sliding spline type of slip joint that can minimize or eliminate the occurrence of broken back. Additionally, in some instances, it is desirable to control the amount of force that is required to be exerted in order to effect relative axial movement between the male and female members of the slip joint. It would, therefore, also be desirable to provide an improved structure for a sliding spline type of slip joint that allows the amount of this force to be controlled in a simple and inexpensive manner.